Method and apparatus for manufacturing granular coated webs



24, 19 0 R... MELTQN M. 2,225,877

METHOD AND APPARATUS FOR MANUFACTURING GRANULAR COATED WEBS Filed Sept.-22, 1939 2 Sheets-Sheet l INVENTORS. ROMIE L MELTON RAYMOND c. BENNER ByHENRY P. KHQCHNER ATTORNEY.

Dec. 24, 1940. R. L. MELTON ETAL METHOD AND APPARATUS FOR MANUFAQTURINGGRANULAR COATED WEBS 2 Sheets-Sheet 2 Filed Sept. 22, 1939 INVENTORS,Rob HE L. MELTON B RAYMOND C. BENNER H EN RY LRCHN ER ATTORNEY.

Patented Dec. 24, 1940 METHOD AND APPARATUS FOR MANUFAC- TURING GRANULARCOATED WEBS Itomie L. Melton, Raymond C. Benner, and Henry P. Kirchner,Niagara Falls, N. Y., assignors to The Carborundum Company, NiagaraFalls,

N. Y., a corporation of Delaware Application September 22, 1939, SerialNo. 296,132 11 Claims. (01. 91-33) This invention relates to themanufacture of granular coated webs of such material as paper, cloth andthe like. More particularly, this invention relates to the applicationof the siz ing coat of adhesive to abrasive coated webs and the removalof such adhesive from the projecting points of the abrasive granules.

In the usual process, by which coated abrasive materials have been madefor many years, it has been customary to coat the backing sheet of paperor cloth with a layer of glue or other suitable adhesive and then applya layer of abrasive grains to the adhesively coated sheet. After thisfirst layer of adhesive had set, a sec- 0nd or sizing layer of adhesivewas applied over the layer of abrasive grains in order to more firmlyattach the grains to the web backing. This sizing layer of adhesive wasapplied by means of a rubber covered roll partially immersed andrevolving in a pan of liquid adhesive and contacting with the abrasivecoated surface. When this sizing layer dried or set, the adhesive shrunkaround the bases of the grains and held them firmly in position.

The quantity of adhesive applied by the glue roll was regulated byvarying the pressure of the glue roll against the abrasive coatedsurface and pressure roll and thereby squeezing the layer of adhesive toa desired thickness.

Thus the layer of sizing adhesive was applied as a sheet or blanketalong on top of the layer of abrasive granules. Due to the fluidity ofthe adhesive and the pressure from the rolls, the adhesive flowed downthe sides of the grains and partially filled the space between adjacentgrains to more firmly anchor them to the base coating of adhesive. Whilethis process was effective in anchoring the abrasive granules securelyin place it was disadvantageous in that the entire surface of theabrasive grains remained covered with a film of adhesive and the sharpprojecting points of the grains did not abrade at their maximumefliciency. Furthermore the adhesive coated surface of the granules,which softened by heat, retained particles of abraded material andquickly filled or clogged the spaces between the abrasive granules. Thisreduced the cutting efliciency of the abrasive and materially reducedits effective life. so The above difficulties were even more pronouncedwith the recently developed abrasive paper and cloth commonly known asoriented abrasive paper and cloth in which elongated granules of theabrasive grain have been orient- 55 ed with respect to the surface ofthe backing material, so as to be upstanding therefrom and therefore ina position to afford a maximum cutting or abrading action.

a We have found that the above difficulties of roll sizing can beovercome and the sizing adhesive completely removed from the projectingtips of the abrasive grains by means of a jet or series of jets arrangedtraversely across the web and adapted to direct a stream or series ofstreams of high velocity gas against the abrasive coated surface. Thisgas is suitably heated and/or treated with a solvent of the adhesive sothat it will not set or chill the adhesive when directed against thegrain tips but will drive the adhesive from the uppermost points of thegrains down and around the bases of said grains. Thus the cutting pointsare freed of the deleterious effect of the adhesive film, a strongerbond is produced at the base of the grains and a greater space isprovided between the grains for cutting clearance and the formation ofchips during subsequent 'abrading action.

A better understanding of the invention may be obtained by reference tothe accompanying drawings, in which:

Figure 1 is an enlarged section through a fragment of the abrasivecoated web at one stage of its manufacture;

Figure 2 is a similar section showing a fragment of an abrasive coatedweb in'which the sizing adhesive has been applied in the usual W y;

Figure 3 is a similar section showing a fragment of an abrasive coatedweb embodying our invention;

Figure 4 is a similar section showing a fragment of an abrasive coatedweb embodying an alternative form of our invention;

Figure 5 is a diagrammatic elevation of apparatus for manufacturingabrasive coated materials in accordance with our invention;

Figure 6 is a detailed side elevation of the adhesive applying mechanismshown diagrammatically in Figure 5; and

Figure '7 is a front view of the apparatus shown in Figure 6.

Referring to Figure 3 which illustrates a fragment of an abrasive coatedweb made in accordance with our invention the reference numeral 2indicates the web or backing which may be of any of the usual flexiblematerials such as paper, cloth, vulcanized fiber or a combination ofthese or other suitable materials. Applied to one face of the web is abase coating 3 of adhesive, such as glue, varnish, silicate or syntheticresin. The particles of abrasive grain 4 are shown in oriented orupstanding position with respect to the backing and are so depositedonto the adhesive base coating I by suitable means not shown in thepresent application. The sizing layer of adhesive 8 is depositedprincipally around the base of the upstanding grains 4 1111- ing thebottoms of the valleys and crevices between the adjacent grains. It willbe noted that the tops of the grains are free of the sizing adhesive andthat the sharp projecting points are in condition for most eflicientabrading. Furthermore the sizing adhesive applied to and built up aroundthe bases of the elongated granules fills any depressions orirregularities in the surface of the individual grains and therebyincreases the bonding or supporting action of the adhesive to hold thegrains in position during subsequent use of the abrasive material.

Figure 1 shows a granular coated material prior to application of thesizing or reinforcing layer of adhesive. Only the bottoms of thegranules 4 are in contact with the base layer of adhesive 3. This givesa very limited and insufficient support to the abrasive granules tomaintain them against lateral pressure and grindin stresses when thecoated web is used as an abradant. It is necessary therefore to applyadditional adhesivearound the bases of the abrasive granules 4 so as tomore firmly anchor them to the base coating and web backing material 2.

Figure 2 shows a granular coated web produced by the usual process, inwhich a blanket of adhesive 5a was applied over the granular coatedsurface and permitted to flow down between the graips of its own accord.The tips of the granular particles 4 are covered with a film of adhesiveindicated by the reference 9. This film of adhesive is very detrimentalwhen the coated material is used for abrasive purposes, since the tipsof the grains are capped with the adhesive. In addition to covering thesharp points of the abrasive material, many adhesives soften duringactual grinding, causing retention of abraded material and clogging ofthe spaces between the grains. This renders the abrasive material unfitfor further use.

The preferred procedure in manufacturing granular coated webs inaccordance with our invention will now be described. The previouslycoated abrasive material, such as that illustrated by Figure 1, is movedfrom suitable drying racks (not shown) by means of the suction drum H,passed around the rubber-covered idler rolls l2, l3 and I4, and betweenthe adhesive roll l5 and cooperating pressure roll IS. The rubbercoveredadhesive roll I5 is partially immersed and revolves in the liquidadhesive contained in the pan l'l so that a layer of sizing adhesive isapplied to the abrasive side of the coated web. The pressure roll i 6 isadiustably supported above the adhesive roll and provided with adjustingmeans (see Figure 6) whereby the spacing between the rolls may be variedand thereby regulate the quantity or thickness of the layer of adhesiveapplied to the abrasive side of the coated web.

After passing between the adhesive applying rolls l5 and I6, the coatedweb is moved past a jet of high velocity gas issuing from the adjustableorifice 3l of the air knife generally indicated by the reference numeral30. This jet of high velocity gas serves to drive the freshly appliedlayer of adhesive from the tips of the abrasive grains and cause it toflow down and around the bases of the grains.

The coated web then passes over the suction drum 40 and idler roll 4| toa suitable drying rack, where it is formed in loops by the festooningdevice 42 and hung on the supporting bars 43 m a drying or curingchamber to fully set the adhesive. After drying or curing, the coatedweb is taken down from the rack and cut into pieces of various sizes andsold.

Referring now to Figures 6 and 7, the operation of the gas jet will bedescribed in more detail. The adhesive pan I1 is supported by a suitableframe 20, which also supports the adhesive roll IS in such a manner thatsaid roll revolves in a liquid adhesive and applies afiim or layer ofsaid adhesive to the coated web I. The pressure roll [6 is alsojournaled on the frame 20 and adapted to be adjusted vertically by meansof the handwheel 2| and screw-threaded shaft 22. Such verticaladjustment of the pressure roll l6 varies the spacing between the coatedweb I and the adhesive roll l5 and thereby regulates the thickness ofthe layer of adhesive applied to the moving web. With a wide spacingbetween the rolls, a thick layer of adhesive will be applied, and with aclose spacing, a relatively thin film of adhesive willbe applied.

The gas jet 30 is mounted on the bearing 23 by a suitable bracket 24 andmoves up or down with any vertical adjustment of the pressure roll I8.Thus theadjustment of the jet with respect to the surface of the coatedweb remains constant regardless of any vertical adjustment of the rolll6. However, the jet is adjustable with respect to the roll l6 and web Iand means are provided for both angular and horizontal movement of thejet 30. Cradle supports 25 are suitably mounted in gibs 26 secured tothe bracket 24 and adapted to be moved horizontally by means of thesmall handwheel 21 and screw-threaded shaft 28 which are journaled onthe bracket 24 and engage a threaded portion of the base of the saidcradle 25.- By loosening the clamping bolt 29, the jet 30 may be tiltedby means of the handle 33 to any desired angle so that the impingementof the gas stream against the coated web can be at an angl of thereto orat any desired oblique angle. x

The thickness of the gas stream 3| issuing from the jet 30 may beadjusted by means of the bolts 32 which regulate the orifice opening ofthe jet 30. This orifice opening is readily adjustable from .002" toapproximately .025" and may extend the full width of the web I, or, ifdesired, a number of such jets may be employed to cover the entire widthof the web. It has been found that too thick a stream of gas causessplattering of the adhesive and does not cause the adhesive to fiow downand around the bases of the grains as desired. Moreover, the impact oftoo thick a jet of high velocity gas will tend to blow over or entirelydislodge the upstanding granular particles on the coated web. We havefound that a jet of approximately .005 inch in thickness is satisfactoryfor most purposes, though with drastic changes in size of granularparticles, it may sometimes be necessary to increase or decrease theorifice opening. We have also found that the leading edge of the gasorifice should preferably be spaced from about A; inch to I; of an ablydesigned jetat' relatively low gas pressures ranging from about 2 to 15pounds per square inch gage and when an orifice opening of approximately.005 of an inch is employed. The gas velocity, and hence gage pressure,required will, of course, depend upon the character, conditionandthickness of the particular adhesive being used. With thick viscousadhesives, a high gas pressure will be required, and with thin or lessviscous adhesives, a relatively lower pressure will be required to clearsuch adhesive from the tips of the granular particles and produce asupporting mound of adhesive around the base of the granules.

We have found the character and composition of the gas stream to be ofparticular importance in carrying out the method of the presentinvention. With adhesives that harden by evaporation of a solvent, wefind it advisabl to introduce a solvent of said adhesive into the gas toprevent setting of the adhesive before it is cleared away from the tipsof the granules or built up around the bases thereof. When usingthermoplastic adhesives, we may heat the gas sufliciently to preventpremature chilling and hardening of the adhesive, and with certainadhesives w may add both a solvent and heat to the gas. Hide or animalglue, which falls in the latter classification,

is the adhesive most generally used in the coated abrasive industry and,for this reason, will be discussed in more detail. Such hide glue isapplied to the coated web at a temperature of approximately 150 F. andjells very quickly when the temperature drops much below 140 F., or ifthere is any substantial evaporation of moisture. If the adhesive ispermitted to become set or j-elled, it cannot be properly removed fromthe tips or cutting points of the grains. For this reason it isnecessary that the gas stream directed against the coated web behumidified with water vapor, which is a solvent for the glue, and heatedto a temperature of 150 F. or above. In actual practice we have found itconvenient to use a mixture of heated compressed air and steam. Thecompressed air is heated to approximately 150 F. by means not shown, andsufficient steam I mixed therewith to saturate the air with watervapor.. It is necessary that the compressed air 'and steam be thoroughlymixed and, for this reason, a separate mixing chamber (not shown in thedrawings) is provided. We have found in certain instances that dry steammay be used alone as the gaseous medium, but for most purposes, it isdesirable to use a mixture of compressed air and steam.

Certain adhesives, such as varnishes and synthetic resins of the alkyd,urea and phenol formaldehyde types, become softer and more liquid duringthe initial heating period. With these adhesives we prefer to use hotcompressed air as the gaseous medium and to heat the air to atemperature of 100 F. to 300 F., depending upon the particular solventemployed in the adhesive used.

We have also found that the character of the coated abrasive materialproduced by the hereindescribed process can be altered by varying theangle of impingement and velocity of the jet.

This jet of high velocity gas serves to drive the film of freshlyapplied adhesive from the tips of the abrasive grains and cause it toflow down and around the bases of the grains. The force of the Jetproduces a depression, indicated by the reference numeral 8 in Figure 3of the drawings, in the adhesive film 5 between adjacent grains andforces the film of adhesive up along the sides of the grains, asindicated by reference I, thereby surrounding the base of eachindividual granule in a mound of adhesive. When the angle of impingementof the jet is approximately 90 with respect to the surface of the coatedweb, the depression 6 of the adhesive film is approximately midwaybetween adjacent grains, as shown in Figure 3. In an abrasive article ofthis character, the granules are supported against lateral displacementin an equal manner regardless of which direction the coated web is movedduring subsequent grinding action.

By varying the angle of impingement of the gas stream so that it strikesthe coated abrasive surface at an oblique angle, we are able to build upthe mound of adhesive to a greater height on one side of the individualgrains than on the other. This feature is clearly illustrated in Figure4 of the drawings, in which the layer of sizing adhesive, generallyindicated by 5, is shown as extending well up the back of the grains 4,

as indicated by the reference In. The depressed portion 6a of theadhesive film is well over near the front of the next succeeding grain.Thus greater reinforcing or supporting action is obtained by a givenamount of sizing adhesive when the abrasive material is moved in thedirection indicated by the arrow 10. This feature is of particularimportance in connection with abrasive belts used in grinding wood,metals and other materials, and increases the rate of cut and effectivelife of the article to a marked degree. Grindposition or degree oforientation of the grains with respect to the web backing. For thisreason, we provide means for readily adjusting and maintaining the angleat which the jet of gas is directed .at the surface of the adhesivesizing coating 5 on the web I. The jet may be adjusted through a widearc, as indicated by the arrow in Figures 5 and 6, by loosening theclamping bolt 29 and rotating the jet in the journals of the bracket 25.Such movement is facilitated by the handle 33, and when the angle isproperly adjusted, the jet is securely locked in position by tighteningthe bolts 29. In producing coated abrasive material, such as that shownin Figure 4, we have found that satisfactory results are obtained whenthe angle of impingement of the gas stream is between 20 degrees and '75degrees with respect to the surface of the coated web. Moreparticularly, it has been found that the best results are obtained whenthe angle between the jet and the web is approximately 50 degrees.

Since the stream of gas strikes the coated web with appreciable force,we have found it desirable to set or cure, at,least partially, the basecoating of adhesive 3 before subjecting the abra-.

sive coated web to the further treatment of a sizing coating ofadhesive, as described in the present application. Such curing orsetting of the base coating is effected in a suitable curing zonethrough which the web is moved prior to passing over the drum II. Thisinitial set or cure of the base coating prevents the upstanding abrasivegranules 4 from being laid flat or entirely dislodged by the forceof thegas stream. However, any loosely adhering or improperly attachedgranules are removed from the coated web.

' Other advantages in the herein-described process for applying thesizing layer of adhesive, to

abrasive coated articles will be apparent from a comparison of thesections of the coated webs illustrated by Figures 2, 3 and 4. Thegranular particles 4 are very irregular in shape and surface contour,particularly so with abrasive particles,

so that a layer of sizing adhesive applied in the ordinary mannerentraps air around the bases of a large portion of the grains. In Figure2, which shows a section of granular material made by the usual process,reference numerals 8a, 8b, 8c and 8d indicate voids around the bases ofthe grains 4 which are not filled with adhesive. These voids are causedby the fact that a sheet or blanket of liquid adhesive is applied to thegranular coated web in the usual process and the fluidity of theadhesive and pressure of the rolls are the only forces acting to causethe adhesive to fill the interstices between adjacent grains. Since theadhesive is fluid at the time of application, it does tend to fiow downthe sides of the granules to the bases thereof. Any crevices, however,are not properly filled because of the surface tension of the blanket ofadhesive and the air entrapped in the said crevices. Obviously, thesevoids, such as 811, materially weaken the anchorage of the granules andwhen the coated material is used as an abrasive, the grains are brokenaway from the backing before their useful life is spent.

In the granular coated material produced by the present process andillustrated by Figures 3 and 4, the above difficulties have beenentirely eliminated. In addition to driving the film of adhesive fromthe tips of the granules, the force of the solvent treated gas stream issufficient to fiow the adhesive into any crevices at the base of saidgrains and to displace any air which may have been entrapped therein.

While we have specifically illustrated and described the preferredembodiment of our invention, it is to be understood that the inventionmay be otherwise embodied and practised within the scope of thefollowing claims.

We claim:

1. The method of manufacturing granular coated webs which comprises thesteps of applying a layer of liquid adhesive to the granular surface ofa web previously coated with granular particles and then directing ahigh velocity stream of gas against the said adhesive layer whereby thepeaks of saidgranular particles are cleared of said adhesive.

2. The method of manufacturing granular coated webs which comprises thesteps of applying a layer of liquid adhesive to the granular surface ofa web previously coated with granular particles and immediatelythereafter directing a high velocity jet of gas against the saidadhesive layer whereby said adhesive is driven from the peaks of saidgranular particles and deposited around the bases thereof.

3. The method of manufacturing granular the bases thereof.

4. The method of manufacturing granular coated webs which comprisesthesteps of applying a layer of liquid adhesive to the granular surfaceof a web previously coated with granular particles and directing againstthe said adhesive layer a high velocity jet of gas emerging from anorifice extending across the full width of said web whereby saidadhesive is driven from the peaks of said granular particles.

5. The method of manufacturing granular coated webs which comprises thesteps of applying a layer of liquid adhesive to the granular surface ofa web previously coated with granular particles and directing againstthe said adhesive layer a high velocity stream of gas of .002 to .025inch in thickness and extending across the full width of said webwhereby said adhesive is driven from the peaks of said granularparticles.

6. The method of manufacturing granular coated webs which comprises thesteps of applying a layer of liquid adhesive to the granular surface ofa web previously coated with granular particles and directing againstthe said adhesive layer a high velocity stream of gas emerging from anorifice under gage pressure of 2 to 15 pounds per square inch, saidorifice having an opening of .002 to .025 inch and extending across thefull width of said web, whereby said adhesive'is driven from the peaksof said granular particles.

7. The method of manufacturing granular coated webs which comprises thesteps of applying a layer of liquid adhesive to the granular surface ofa web previously coated with granular particles and then directing at anoblique angle to said adhesive layer a high velocity stream of gaswhereby said adhesive is driven from the peaks of said granularparticles and deposited around the bases thereof forming a suppo'rtingmound of adhesive located principally on one side of said granularparticles.

8. The method of manufacturing granular coated webs which comprises thesteps of applying a layer of adhesive of predetermined thickness to thegranular surface of a web previously coated with granular particles andthen directing against said adhesive layer a high velocity stream of gaswhereby said adhesive is driven from the peaks of said granularparticles and deposited around the bases thereof.

9. The method of manufacturing granular coated webs which comprises thesteps of applying a layer of adhesive of predetermined thickness to aweb previously coated with granular particles, the thickness of saidadhesive layer being that required for the particular size of the saidgranular particles, and then directing against said adhesive layer ahigh velocity stream of gas whereby all of said adhesive is retained onthe web but is driven from the peaks of said granular particles anddeposited around the bases thereof.

10. Apparatus for the manufacture of granular coated webs comprising, aframe member, means for moving and supporting a granular coated web, anadhesive roll Journaled on said frame and adapted to apply a layer ofadhesive to iii) said granular coated web, adjustable supporting membersmounted on said frame, a pressure roll mounted in closely spacedrelationship to said adhesive roll and :Iournaled on said adjustablesupporting members, means for moving said roll supporting members toregulate the spacing between the coacting pressure and adhesive rolls,

whereby the thickness of the adhesive layer applied to the web may becontrolled, and a gas jet also mounted on said pressure roll supportingmembers to direct a high velocity stream of gas against said adhesivelayer, said apparatus being adapted to maintain a definite spacedrelationship between said gas jet and the surface of said adhesivecoated web regardless of adjustments in spacing between said adhesiveand pressure rolls.

11. Apparatus for the manufacture of granular coated webs comprising, aframe member, means for moving and supporting a granular coated web, anadhesive roll ioumaled on said frame and adapted to apply a layer 01'adhesive to said granular coated web, adjustable supporting membersmounted on said frame, a pressure roll mounted in closely spacedrelationship to said adhesive roll and journaled on said adjustablesupporting members, means for moving said roll supporting members toregulate the spacing between the coacting pressure and adhesive rolls,whereby the thickness of the adhesive layer applied to the web may becontrolled, a gas jet also mounted on said pressure roll supportingmembers to direct a high velocity stream of gas against said adhesivelayer, and means for varying the spacing between said air jet and saidpressure rcll, said apparatus being adapted to maintain a definitespaced relationship between said gas jet and the surface of saidadhesive coated web regardless of adjustments in spacing between saidadhesive and pressure rolls.

ROMIE L. MELTON. RAYMOND C. BENNER. HENRY P. KIRCHNER.

